1. Field of the Invention
This invention relates to an improved ball valve of a bottom entry stem type having a positive, improved interfitting latching or splined engagement of its operating stem and particularly, to a valve in which its operating stem has a substantially fully side-enclosed, detachable, tongue and recess slide-in fit within its ball. Another phase of the invention relates to a fail-safe ball valve construction in which positive elimination of stem outshoot is assured, and an improved sealing action is attained at its stem gland and which may be effective even when the gland nut is loosened.
2. Description of the Prior Art
There have been two types of ball valve assemblies from the standpoint of the operating stem. One type which facilitates the removal of the internal elements has been designated as a top entry stem type. The other has been designated as a bottom entry type and has the advantage of being safer from the standpoint of avoiding the danger of pressure-forcing the stem out of the valve body. The top entry type is more likely to develop leakage, is dangerous in that it permits stem shoot-out under pressure, and presents difficulty in endeavoring to turn the ball to a closed position when the mounting gland becomes loose, fails or releases the stem.
However, the bottom entry type which has an outer entry to the ball has been disadvantageous from the standpoint of an endwise-floating, upstream-downstream type of mounting engagement between the stem and the ball. This is inherent due to the heretofore seeming need for a so-called endwise-extending, open-end or through-extending latching slot in the outer wall of the ball to enable its entry and release from the latching end of the stem when the ball is to be entered into an operating relation within and to be removed from within the body. One type of slot has a depth that is at a maximum at its mid or central portion and that slopes in a curved bottom path of decreasing depth towards its opposite, longitudinal open end portions. Another type is substantially planar between its open ends along its endwise extending bottom portion. Both permit endwise float of the ball with respect to the stem.
More specifically, it is customary in the bottom entry stem type of valve to provide an elongated slot in the ball which is open at its ends from the cross sectional center of the slot in an elongated manner towards both ends thereof, outwardly into the rounded or spherical circumferential wall surface of the ball. See, for example, FIG. 5 of Alvarez U.S. Pat. No. 3,614,056. The extent of the slot is limited by the size of the ball to avoid interference with the two surfaces which are adapted, with opposed, end-positioned, annular gaskets, to always seat on its rounded surface and close-off the valve. Such a construction inherently provides an endwise-slidable, frictional side wall fit between two opposed elongated sides of endwise-outwardly reduced depth of the latching slot in the ball, and thus of cooperating latching flange engagement of the stem with the slot. This is accentuated when both the base of the slot and of the stem flange have an upwardly curved slope endwise thereof. There is thus the danger of spalling the side edges of the ball by a tendency, during heavy duty operating conditions, for the latching flange of the stem to turn with respect to a lesser depth end portion of the opposed sides of the slot. This is particularly true, since the ball has a floating relationship within the body, endwise in the direction of fluid flow, either in its open position (See FIG. 1 of Alvarez) or in its closed position (see column 2, lines 47 to 52, of Scaramucci U.S. Pat. No. 3,397,861), and may move into an off-centered relation with respect to the latching flange, such that only a minimum opposing side wall surface depth is in actual engagement.
It has heretofore thought to be necessary to provide an endwise-open, elongated slotted portion to permit the ball to be removed from a bottom entry stem that is removable only from within a flow opening in the body. Also, it has heretofore thought to be necessary to provide a certain amount of endwise play in the seating relation of the ball with respect to its end-positioned seating-sealing gaskets, but such play produces wear and tear on the gaskets and increases the danger of spalling damage to the ball under heavy duty operating conditions.